A US federal court judge has ruled that Novell, and not the SCO Group, is the rightful owner of copyrights covering the Unix operating system, a ruling that should have a major effect on a number of lawsuits, including SCO's actions against Novell, IBM and Red Hat.

The 102-page ruling by Judge Dale Kimball refuted many of SCO's claims against Novell, and seemed to remove the basis for its lawsuit against IBM. SCO had previously charged that the Linux operating system was an unauthorised derivative of Unix, which it claimed to have purchased from Novell in 1995.

"The court's ruling has cut out the core of SCO's case and, as a result, eliminates SCO's threat to the Linux community based upon allegations of copyright infringement of Unix," Joe LaSala, Novell's senior vice president and general counsel, told The New York Times.

The Unix operating system was developed by AT&T researchers at Bell Labs from 1969. While it has been a long-time favourite in server and mainframe systems, it never gained a great foothold in the personal computer business until the Linux variant was developed in the early 1990s, and Apple started to base their Mac OS on a version of Unix.

Figures from the open-source industry also see the ruling as a boost to their business.

"This is a meaningful message in terms of people adopting open-source software," James Zemlin, executive director of the Linux Foundation, told The New York Times. "This says that Linux is a safe solution and people can choose it with that in mind."